when working on very specific things i also learned to iron the patterns
you can preshrink dry clean only fabric by rolling it in slightly damp (NOT wet) towel and patting it, then hanging it dry.
to add to making fabric thread perfect, it may still be "off grain" after that process.
you can tell by folding the fabric "hot dog" way, selvage to selvage, and if the thread perfect edge stays level with it's self and the selvages both end at the same spot, then it is on grain, if one side is longer, and the thread perfect end of the fabric makes a V at the fold, it needs to be tugged on the bias to straighten that out.
doing that prevents you from sewing the whole thing, and having your side seams spin around like a twisty cone after you wash it once.